Superconsolidated conditioned reflex—A highly adaptive system of behavior

Superconsolidated (2500–3000 combinations), long-trained (two to three years), specialized (per I. P. Pavlov), instrumental alimentary conditioned reflexes were investigated in cats. It was demonstrated that such conditioned reflexes are unusually rapidly extinguished, despite the classical notion of extinction, according to which the more consolidated the conditioned reflex the more difficult it is and the longer it takes to extinguish it. Thus, in the very first experiment, stable extinction of the conditioned reflex commenced after two to seven (in different animals) presentations of the conditional stimulus without reinforcement, and 15–20 “zeros” in a row in relation to the conditioned reaction could be obtained. The rate of extinction essentially did not depend on the individual features of the animals or the level of alimentary motivation. The data obtained make it possible to set such reflexes apart in a special new category of conditioned reflexes, which apparently have a different neurophysiological and structural control base than the “younger” conditioned reflexes commonly studied in the laboratory. Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 45, No. 3, pp. 458–463, April–May–June, 1995.     

The conditioned reflex: Detectors and command neurons

The conditioned reflex is characterized by plasticity supporting bilateral selective connections between its input and output. In simple nervous systems, input stimuli are represented by selective detectors connected to command neurons by plastic synapses whose activity increases on learning and decreases on extinction. The process of associative learning occurs when excitation of the detector and the command neuron coincide. Short-term memory in a plastic synapse is associated with phosphorylation of postsynaptic receptor molecules and does not require protein synthesis. Long-term memory is associated with early gene expression, structural genes, and protein synthesis. The simple “detector-command neuron” association has increased in complexity during evolution. At the input, predetector interneurons activating a specific detector converge on the command neuron: the command neuron determines the selectivity of the mechanisms of conditioned reflexes for complex stimuli. The output mechanism has also become more complex: command neurons have become more specialized and premotor interneurons have appeared between them and motor neurons, excitation of premotor neurons being passed to groups of motor neurons responsible for the configuration of the behavioral act. Conditioned reflexes combining more complex signals at the input with more flexible results at the output allow a diversity of behavioral acts. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 57, No. 1, pp. 5–22, January–February, 2007.     

Corticohypothalamic relationships during the development and realization of the conditioned reflex

The influence of motivational, emotiogenically positive and emotiogenically negative structures of the hypothalamus on the development and realization of conditioned reflexes was investigated in the experiments on dogs, cats, and rats. It was shown that the motivational structures primarily increase excitability of cortical neurons during the development of the conditioned connection, while the emotiogenically negative and emotiogenically positive structures increase the efficiency of synapses. A high degree of correlatedness of the averaged evoked responses to the conditional stimulus in the hypothalamus and new cortex is characteristic for the consolidated conditioned reflex. Direct stimulation of the motivational-alimentary zones of the hypothalamus reproduce food-procuring conditioned reflexes in dogs, while stimulations of the emotiogenically negative zones reproduce defense conditioned reflexes. Stimulation of the emotiogenically positive zones does not reproduce either; however, an intensification of the activity of neurons of the hypothalamus was recorded in rats during the successful accomplishment of the conditioned reaction of avoidance of an aversive stimulus. In cats which are capable of restraining a conditioned motoric reaction for the sake of obtaining a preferred food, the “motivational”, long-latency functional connections between neurons of the lateral hypothalamus and the prefrontal cortex predominate. Short-latency “informational” connections predominate in the “impulsive” cats. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 43, No. 2, pp. 12–21, March–April, 1993.     

Effects of microinjection of scopolamine into the neostriatum of rats on performance of a food conditioned reflex at different levels of fixation

Chronic experiments performed on 32 Sprague-Dawley rats using a movement-feeding operant reflex (Skinner box) model showed that microinjection of scopolamine into the neostriatum had effects on this reflex which depended on the stage of learning. In animals with weakly fixed reflexes (prior to reaching the stage of memory consolidation), bilateral microinjection of 0.3 μg of scopolamine into the caudate nucleus completely inhibited the reflex for a prolonged period of time. When the operant habit was well fixed, bilateral microinjection of the same doses of scopolamine into the neostriatum had no effect on the reflex. These results suggest that the neostriatum cholinergic system is critically involved in forming the motor engram. The cholinergic system of the caudate nucleus either takes no part in realizing the well-fixed conditioned reflex movement response and/or other forebrain structures are involved in the reflex, compensating for the disturbance in neostriatal cholinergic function. I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg. Translated from Fiziologicheskii Zhurnal im. I. M. Sechenova, Vol. 81, No. 8, pp. 139–146, August, 1995.     

Spatial-temporal organization of the functions of cortical neurons in a conditioned reflex to time

The impulse activity of neurons in the motor cortex of cats during the development of a conditioned food-procuring reflex in relation to a time interval of 2 min (CRT) was analyzed. It was demonstrated, by comparing the behavioral and neurophysiological correlates of the formation of the conditioned food-procuring reaction, that its formation is accompanied by extremely complex systemic transformations which are different for neuronal micro- and macrostructures. The systemic processes in the micro- and macrostructures differed with respect to the specific characteristics of spatial distribution, and with respect to the number, strength, and stability of the manifestation of the functional connections. The capacity of the neurons for functional orientation even at the initial levels of the formation of the reaction, an increase in the per cent of incidence of functional connections in the second half of the conditioned reflex interval, and the substantial destabilization of all neuronal units at the last, highest level of formation of the conditioned reflex food-procuring reaction were common to the micro- and macrostructures in this form of learning. M. V. Lomonosov Moscow State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 44, No. 4–5, pp. 738–750, July–October, 1994.     

Comparative study of the roles of ACTH and β-endorphin in regulating conditioned reflex activity in the hedgehog

Data on the relative effects of the neurohormone ACTH_1–39 and the opioid peptide β-endorphin on conditioned reflex activity in the hedgehog are presented. It was demonstrated that administration of ACTH (30–50 μg/kg s.c.) led to facilitation of learning and strengthening of memory processes (conditioned reflex traces). ACTH promoted strengthening of movement, orientational-investigative, and intersignal activities, produced hyperalgesia, and blocked the effects of naloxone. Administration of β-endorphin (30–40 μg/kg s.c.) lengthened the latent periods of conditioned reflexes, produced a pronounced analgesic effect, and reduced movement and intersignal activities. The effects of β-endorphin were eliminated by dosage with naloxone. Administration of β-endorphin blocked the inhibitor effects of stimulation of the limbic cortex; doses of ACTH produced partial release of inhibitory effects. The differences between the effects of ACTH and β-endorphin on higher nervous activity are discussed, as are the possible mechanisms of these effects. Laboratory for Comparative Cerebellar Physiology (Director R. A. Grigor'yan), I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 81, No. 12, pp. 20–30, December, 1995.     

Effects of BT-melanin on recovery of operant conditioned reflexes in rats after ablation of the sensorimotor cortex

An increase in corticofugal plasticity was demonstrated in adult rats after unilateral ablation of the sensorimotor cortex accompanied by intramuscular administration of low concentrations of BT-melanin solution. The result was acceleration of the process of compensatory recovery in the central nervous system, this being supported by the rapid recovery of a previously acquired operant conditioned reflex and movement of the paralyzed limb as compared with control animals. It is suggested that compensation of the motor deficit arising after ablation of the sensorimotor cortex is mediated by the ability of the two major motor systems of the brain — the corticospinal and the corticorubrospinal — to exhibit mutual substitution of their functions. This phenomenon of the functional switching of descending influences also occurred in rats of the control group not exposed to BT-melanin. However, the difference between the recovery times of the operant conditioned reflex and limb movement in the control and experimental groups provided evidence of an apparent acceleration in these processes as a result of BT-melanin. These results suggest that low concentrations of BT-melanin may have applied uses. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 56, No. 3, pp. 384–391, May–June, 2006.     

The role of the pineal gland in forming a conditioned reflex to time in rats

The effects of pinealectomy and melatonin on time-associated conditioned reflex behavior were studied. Removal of the pineal gland hindered the formation of a conditioned reflex in conditions of a fixed time interval in rats. This was accompanied by a shortening of latency and excursions and an increase in the number of intersignal responses. Administration of melatonin (0.1 mg/kg) had the opposite effects, facilitating the development of the conditioned response to time and limiting motor activity. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 48, No. 1, pp. 54–59, January–February, 1998.     

Monoaminergic amygdalar mechanisms of conditioned reflexes of varied biological modality

Microinjection of dopamine and serotonin into the dorsomedial zones of the rat amygdala led to an increase in the latent period of conditioned defensive and motor-food reflexes, spontaneous motor activity, and the number of pushing movements and the magnitude of the food-grasping reflex. Noradrenalin had no effect on the parameters of the conditioned food reflex but facilitated the conditioned avoidance reflex, reducing its latent period considerably. The results are evidence of the specificity of the neurochemical mechanism responsible for reflexes of varied biological modality at the amygdalar level in rats.     

Human eeg during formation of conditioned reflexes

Summary The EEG changes, with prolonged repetition of conditioned reflexes (elaborated according to the method of defensive and speech-motor conditioned reflexes), were studied in 60 healthy individuals.The reaction of the alpha-rhythm depression observed at the beginning in all of the leads, gradually becomes limited to the area of the motor analyzer, on the side contralateral to the reinforcing movement.Further strengthening and repetition of a conditioned reflex results in a gradual leveling out of the conditioned-reflex electroencephalographic reaction. Such condition may be attained when it becomes very difficult, or even impossible, to detect any changes in the main electric activity of the brain in response to some stimuli, for instance, a coustic ones, although these are still capable of provoking conditioned reflex motor reaction.(Presented by Active Member of the AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 50, No. 9, pp. 11–16, September, 1960     

The cardiac component of conditioned defensive reflexes in dogs

Summary A study was made of the cardiac component of conditioned positive and inhibitory reflexes. Experiments were performed on four dogs in which a set of conditioned reflexes had been developed.Changes in heart rate occurring during the presentation the conditioned signals were largely determined by the type of nervous system and by the general degree of excitation. The signalling significance of the conditioned stimuli, the strength-stimulus relationship, and the nature and stability of the differentiation of the cardiac response were consistent with the motor conditioned reflex.Finally, it was shown that when the motor are respiratory responses were inhibited by 1 mg/kg aminasin, the conditioned signals were not only effective in causing heart rate changes but also retained their signalling significance: when applied during aminasin bradycardia, positive signals increased and inhibitory decreased the heart rate.(Presented by Active Member AMN SSSR A. L. Myasnikov) Translated from Byulleten Èksperimental'noi Biologii i Meditsiny Vol. 49, No. 4, pp. 15–20, April, 1960     

Chaotic components in the high-frequency EEG of rabbit cortex during formation of a conditioned defensive reflex

The chaotic component of the high-frequency EEG of the rabbit cortex was studied during the development of a conditioned defensive reflex to nonrhythmic light stimulation with electric reinforcement applied to the animal's paw. Regular changes in the dynamic parameters of the chaotic component of the high-frequency EEG were demonstrated. Characteristic changes in the asymptotic evaluations of the correlational dimensionality of the attractor of the chaotic component (DCC) of the high-frequency EEG were detected in the cortical regions studied both during the action of the conditioned stimulus and in background conditions before presentation of combinations. These changes affected both the afferent and efferent cortical regions of the conditioned reflex arc, as well as regions not directly addressed by the conditioned or unconditioned stimuli. These results allow the dynamics of changes in the morphofunctional structures of the conditioned reflex to be seen at the cortical level during learning. Significant differences in the early and late stages of conditioned reflex formation were detected. Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 47, No. 5, pp. 858–869, September–October, 1997.     

The electrical characteristics of command and motor neurons during acquisition of a conditioned defensive reflex and formation of long-term sensitization in snails

The mechanisms of the acquisition of a conditioned defensive reflex and formation of long-term sensitization were studied at the level of an analysis of electrical characteristics of defensive behavior command neurons and motor neurons which open and close the pneumostoma. Significant decreases in membrane and threshold potentials were seen in command neurons in response to acquisition of the conditioned defensive reflex and formation of long-term sensitization, along with further decreases in these parameters in snails which were trained after long-term sensitization. Changes, in the critical level of depolarization and amplitude of action potentials were insignificant. The changes observed here provide evidence for an increase in the membrane excitability of command neurons. Similar changes were not seen in motor neurons. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I.P. Pavlova, Vol. 48, No. 6, pp. 1004–1013, November–December, 1998.     

Summation of excitations during uncoditioned reinforcement of a conditioned reflex

Summary After conditioned motor defensive reflexes had been developed in dogs using Protopopov's method, a comparison was made of the effects produced by unconditioned electrical cutaneous stimuli given either separately or together with conditioned stimulus. The strength of the unconditioned reinforcement ranged from threshold to submaximal values. It was shown that during unconditioned reinforcement there is a summation of the conditioned and unconditioned reflexes, two weak reflexes usually giving an effect which is greater than the sum of the separate values, while two moderate reflexes give a result which is almost equal to the summed effect. A strong and a weak or two strong reflexes give an effect which is equal to or slightly greater than the value of the strong reflex. the results obtained show that in the summation there may be either facilitation or occlusion.(Presented by Active Member AMN SSSR V. N. Chernigovskii) Translated from Byulleten' eksperimental'noi biologii i meditsiny Vol. 49, No. 1, pp. 3–7, January, 1960.     

The role of motivation in the performance of conditioned reflex switching of a maze skill in response to substitution of food reward quality in ants of the species Myrmica rubra

The characteristics of learning in ants — active Myrmica rubra foragers — were studied in a maze at different levels of colony carbohydrate food need with reinforcement consisting of carbohydrate (sugar syrup) or protein (pupae of Lasius niger ants). Measures of the maze skill during learning reinforced with syrup were somewhat worse than those during learning reinforced with pupae, especially in terms of time-based measures. Ants were able to modify the acquired conditioned reflex reaction when the quality of reinforcement changed. At high levels of food need (“ hungry” colony), substitution of syrup with larvae and vice versa was followed by transformation of the previously formed skill; this occurred at both experimental periods (training and testing). At low levels of motivation (“sated colony”), the optimized maze habit formed with protein reinforcement was replaced in the test with carbohydrate reinforcement by a “stochastic,” unoptimized behavior with a dominance of investigative activity. These experiments demonstrated that conditioned reflex switching can occur in higher social insects — ants — in which the different forms depend on the level of colony need for food and, respectively, on the level of social food-related motivation of forager ants. The special importance of using the switch activating the corresponding motivational system before changing the reinforcement food quality is emphasized. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 55, No. 6, pp. 833–841, November–December, 2005.     

Changes of conditioned reflexes in dogs during inhalation of ether in low concentrations

Summary The object of study was the dynamics of conditioned secretory food reflexes in dogs during 20–60 min inhalation of a 1–2% ether-oxygen mixture. It was found that a 1% ether mixture, without causing a change in general dogs' behavior, provokes a reduction of the conditioned reflex to a weak stimulation and disinhibition of the capacity for differentiation. The total intensity of conditioned reflexes usually declines by 4–65% below the control level. Upon inhalation of a 2% ether mixture, dogs develop a motor unrest. The conditioned reflexes are reduced in all dogs, the capacity for differentiation is disinhibited, and the ultraparodoxical and paradoxical phases come on the scene. The restoration of conditioned reflexes following inhalation of ether in small concentrations occurs on the 2nd-15th day.(Presented by Active Member of the Academy of Medical Sciences of the USSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 61, No. 1, pp. 63–65, January, 1966     

An automatic transmitter of conditioned and unconditioned stimuli for developing conditioned reflexes in small animals

Summary We developed an apparatus which will permit automatic transmission of conditioned and unconditioned stimuli for the development of conditioned reflexes in small animals. The step-finder, the synchronous motor, the switch board and all the numerous details are well-illustrated.This transmitter facilitates laboratory investigations and permits a very objective and precise approach to the animals. It may be connected either to electric or pneumatic feeding devices and may be used in standard conditioned reflex boxes.Presented by Active Member Acad. Med. Sci. USSR K. N. Bykov     

Mechanisms of the formation of reactions of cat motor cortex neurons associated with the triggering of the conditioned placing reflex: A hypothesis

The possible physiological mechanisms of the generation of reactions by neurons of the cat motor cortex during the triggering of a conditioned placing reflex are examined. It is hypothesized that neurons of the motor cortex function as a neuronal generator similar to the spinal generator of locomotion, which can be triggered through ion channels that are controlled by NMDA-type glutamate receptors. The conditions necessary for the opening of these channels under the influence of glutamate are achieved by the conditioned “arousal reaction”, the neurochemical equivalent of which is an intensification of the cholinergic and noradrenergic and/or serotoninergic afferentation to the cortex. M. V. Lomonosov Moscow State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 44, No. 6, pp. 963–973, November–December, 1994.     

A possible mechanism for the effect of modifiable lateral inhibition in the striatum on the selection of conditioned reflex motor responses

A mechanism is proposed for the effects of striatal dopamine-modifiable lateral inhibition on the selection of conditioned reflex motor responses. According to this mechanism, activation of dopamine D1 (D2) receptors on strionigral (striopallidal) neurons facilitates long-term depression (potentiation) of the inhibitory inputs simultaneously with potentiation (depression) of the excitatory inputs, of sufficient strength to open NMDA channels. For “ weak” excitation, insufficient to open NMDA channels, the modification rules were of the opposite sign. Activation of presynaptic D2 (D1) receptors leads to decreases (increases) in GABA release from strionigral (striopallidal) axon terminals innervating strionigral (striopallidal) cells. As a result, dopamine-modifiable lateral inhibition simultaneously increases both the potentiation (depression) of the excitatory inputs to “strongly” activated strionigral (striopallidal) neurons, increasing (decreasing) their activity, and increases the depression (potentiation) of the excitatory inputs to the “weakly” activated strionigral (striopallidal) neurons, decreasing (increasing) their activity. Subsequent reorganization of neuron activity in the cortex-basal ganglia-thalamus-cortex circuit facilitates selection of conditioned reflex motor responses by further increasing (decreasing) the activity of those motor cortex neurons which were “strongly” (“weakly”) excited by the striatum in conditions of dopamine release in response to the conditioned stimulus. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 55, No. 4, pp. 444–458, July–August, 2005.     

Identification ofDrosophila mutant with memory defects after acquisition of conditioned reflex suppression of courtship

Four lines were selected from a collection of 33 lines prepared by P insertion mutagenesis using a single-copy P-element system; the males of these four lines showed memory defects after acquisition of conditioned reflex suppression of courting. In two lines (P171 and P95), the dynamics of retention of the conditioned reflex in the repeated impregnated-female courting test were similar to those of known short-term memory mutantsdnc andrut. In line P153, the dynamics were more reminiscent of the memory dynamics in a known medium-term memory mutant,amn. In line P124, the learning index was insignificant immediately after training was completed, which may indicate that this line was unable to acquire conditioned reflex suppression of courting. Determination of the positions of the P elements (P171: 48A-B; P153: 49B-C; P124; 67B–68A; P95: 77C-D) showed no correspondence with previously known mutations producing memory lesions. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 85, No. 1, pp. 84–92, January, 1999.